Railway-traffic-controlling apparatus



June 26, 1928.

L. V. LEWIS RAILWAY TRAFFIC CONTROLLING APPARATUS Original Filed April 21. 1921 3.Sh69tS-Sh6et INVENTOR 3 Plate Curmnf] June 26, 1928.

L. V. LEWIS RAILWAY TRAFFIC CONTROLLING APPARATUS Original Filed April 21. 1921 5 s s t 2 INVENTOQR I Wifi:

June 26, 1928. 1,674,782

L. v. LEWIS RAILWAY TRAFFIC CONTROLLING APPARATUS Original Filed April 21. 1921 3 s t -sh t, 3

INVENTOR K. WWI/u,

Mar/6,2,

Patented June 26, 1928.

UNITED STATES PATENT OFFICE.

LLOYD V. LEWIS, OF EDGEWOOD BOROUGH, PENNSYLVANIA, ASSIGNOR TO THE UNION SWITCH & SIGNAL COMPANY, OF SVJISSVALE, PENNSYLVANIA, A CORPORATION OF PENNSYLVANIA.

RAILWAY-TRAPFIG-CONTROLLING APPARATUS.

Continuation of application Serial No. 463,415, filed April 21, 1921.

This application filed July 26, 1923.

Serial No. 653,886.

My invention relates to railway traflic controlling apparatus, and is particularly adapted to apparatus of the type wherein signals are controlled by the presence and absence of trains through the medium of track circuits.

I will describe several forms of apparatus embodying my invention, and will then point out the novel features thereof in claims.

The present application is a continuation of my copending application filed April 21, 1921, Serial No. 463,415, for railway signaling systems, in so far as the subject matter common to the two is concerned.

In the accompanying drawings, Fig. 1 is a diagram illustrating certain characteristics of an electron tube of the three element type. Figs. 2, 3, 4, 5, 6, 7 and 8 are diagrammatic views showing various forms of apparatus embodying my invention. Figs. 9 and 10 are views illustrating certain electrical conditions in the apparatus shown in Fig. 8.

Similar reference characters refer to similar parts in each of the several views.

Referring first to Fig. 1, the diagram constituting this view relates to an electron tube of the three element type, that is, a tube having a filament, a grid and a plate. The diagram is plotted between plate voltages as abscissae, and plate circuit currents as ordinates, grid voltage being constant. and the diagram comprises three curves based on different values of grid voltage. urve Eg-- is based on a grid voltage which is negative with respect to the filament, curve Ego based on zero grid voltage, and curve Eg-lis based on a grid voltage which is positive with respect to the filament. For any given, grid voltage it will be noted that the plate current increases as the plate voltage increases, provided the plate voltage is positive, that is, provided the plate is positive with respect to the fila inenl. When the plate voltage is negative that is. when the plate is negative with re spect to the filament, then for any value of plate voltage the plate current is zero.

Referring now to Fig. 2, the reference characters 1 and 1 designate the track rails of a railway over which traffic normally moves in the direction indicated by the arrow. These rails are divided into a plurality of track sections, of which only one sew tion AB is shown in the drawing. As here shown, the rails of section AB are electrically isolated from the rails of the adjoining portions of track by insulated joints 2, but any other suitable means for isolating the sections may be employed without departing from the scope of my invention.

Located adjacent the entrance end of the section AB is a signal S which governs trafiic through the section, and which, as here shown, is in the form of a light signal, having two lamps G and R, which lamps when illuminated indicate proceed and stop, respectively.

The section A-B is provided with a track circuit comprising a transformer T, the secondary of which. is connected across the rails adjacent the exit end of the block, and the primary of which is connected with a transmission line 3 which is constantly supplied with alternating signaling current by a generator 4. The track circuit also comprises a transformer H, the primary of which is connected across the rails adjacent the entrance end of the section.

The signal S is controlled by an electron tube D comprising a heated filament 5, a grid 6 and a plate 7. The filament 5 is constantly heated from the secondary 8 of a transformer J, the circuit being from this secondary, through wire 9, filament 5 of tube D, wire 10, filament 5 of a rectifier K, and wires 11 and 12 to transformer secondary 8. The primary 15 of transformer J is con stantly supplied with alternating signaling current from the transmission line 3.

The electron tube D is provided with a grid circuit which is supplied with energy from the secondary of transformer H through wires 24- and 25. It will be seen, therefore, that this grid circuit is energized when the track section AB is unoccupied, but not when this section is occupied by a car or train.

The electron tube D is provided with a plate circuit containing a source of alternating current which as here shown is a secondary 16 of transformer J. This circuit passes from the left-hand terminal of secondary 16, through wire 13, proceed lamp G, wire 14; tube D, wire 10, filament 5 of tube K, wire 11, upper primary winding 17 of a trans former N, and wire 18 to the right-hand terminal of secondary 16. The circuits for tube D are so arranged that when the track circuit is unoccupied the grid 6 is positive with respect to the filament at the same instant that the plate 7 is positive with respect to the filament 5. .Vhen the track section AB is occupied, the grid circuit is tie-energized, that is, the grid voltage is zero so that the characteristics of the tube are represented by the curve B90 in Fig. l. I will assume that the plate voltage is the value represented by the point E7) in Fig. l, and so it follows that the plate circuit current 1,. This current is so small that it is insufficient to light lamp G. When, however. the grid circuit is energized, the characteristics of the tube are represented by the curve Fig-f in Fig. 1, and so the plate circuit current is then 1 This current is relatively large and is sufficient to light the lamp G.

To express the same thing in another ay, when the grid circuit is tile-energized current will. flow in the plate circuit, but since the electrons in the space between the plate and filament constitute a negative space charge, they will oppose the applied potential, and the current is so small that it is insufficient to illuminate lamp G. \Vhen, however, grid 6 is positive, its potential will largely neutralize the negative space charge and permit a much larger current to flow so that lamp G will be illuminated. It follows, therefore, that when the track circuit is unoccupied tube D offers a relatively low impedance, that is, is conductive" to current in the plate circuit. so that lamp G is illuminated by pulsating current but when the grid circuit for this tube is deenergized, the tube offers a relatively high impedance to current in the plate circuit so that lamp G is extinguished. In other words. the current which flows in the plate circuit is controlled by the voltage applied to tube D by the grid circuit.

Also associated with signal S is a half wave rectifier K comprising a filament 5 and a plate 7. The filament 5 is constantly heated and as here shown is included in series with filament 5 of tube D, the circuit for which filament is traced hereinbefore. The rectifier K is provided with a plate circuit which is energized from a secondary 26 on transformer J. this circuit being from the left-hand terminal of secondary 26, through wire 19. rectifier K. wire ll, lower primary 17 of transformer N. and wire 20 to the right-hand terminal of secondary 26. As is well understood, current will fiow in this circuit when the plate 7 is positive with respect to the filament 5, but not when the filament is positive with respect to the plate. The impedance of rectifier K is relatively low and is substantially equal to the impedance of tube D when the grid circuit for this tube is energized.

through prin'iary winding 1.7.

The stop lamp R is connected to the secondary 21 of transformer N through wires 22 and It Will be observed that the left-hand terminal of secondary 16 is connected with the plate 7 of tube D, and that the left-hand terminal of secondary 26 is connected with the plate 7 of rectifier K. It follows that when tube D is cr. nductive". the plate circuit for tube D and the plate circuit for rectifier K carry pulsating currents which are in phase. One of these currents flows in one direction through primary winding 1? and the other flows in the other direction The circuits are adjusted in such manner that these currents are substantially equal so that when tube D is condlu'tive.-that is. when lamp G is illuminated, there is a negligible voltage. if any. induced in the secondary 21 of transformer N. so that lamp R is dark. in other words. the effect of the plate circuit of tube D on transformer N is neutralized or counter-ha]anccd by the circuit for th rectifier K. hen the track section A--ll is unoccupied, then signal S indicates pro ceed.

\Vhen a car or train enters section A-li. the supply of current to the grid circuit for tube D is discontinued so that the plate circuit for this tube is rendered ubstantially non-conductive and lamp G is consequently extinguished. The result of this that substantially no current flows in the primary winding 17 of transformer N. The circuit for the rectifier K is not affect d. however. and so the primary winding 17 continues to be supplied with pulsating current. 'lhiz: pulsating current impressed upon the pri-- mary of transformer N will induc an alter hating current in the circuit inzu idiufondary Q] and lamp R. so that lamp R be comes lighted and the signal indicates stop.

Referring now to Fig. 3. the signal .w' is in this instance controlled by two electron tubes D and D each of which comprises a filament 5. a grid 6 and a plate 7. The filzr men s 5 of these tubes are constantly heated by virtue of a circuit which passes from transformer secondary 8.. through wires 2.) and 30. filament f) of tube D. wire filament 5 of tube D and wire 31 to secondary 8. Each electron tube is provided with a grid circuit which receives energy from the secondary of transformer II when the track section A--B is unoccupied. The grid circuit for tube I) passes from the transformer secondary through wires 24 and 24, tube I). and wire 25 to the transformer secondary. The grid circuit of tube D is from the transformer secondary through wires 24' and 27, tube D wire 28. the filament 5 of tube D. and wire 25 to the transformer secondary. It. will he noted that each grid is fit) connected with the righthand terminal of the secondary ot' transformer II, so that at any given instant the potential of these two grids is the same.

The electron tube D is provided with a. plate circuit which passes from the left-hand terminal of transformer secondary 16, through wire 32, proceed lamp G, wire 33, tube D, and wires 30 and 35 to a point 36 in the secondary 16. The adjustment of the circuits associated with tube D is the same as the adjustment of the circuits associated with tube D in Fi 2, that is, the plate voltage is the value in in Fig. 1, and the plate and grid are simultaneolwly positive with respect to the filament. It follows that, as in Fig. 2, when the grid circuit is energized. the plate circuit carries sutlicient pulsating current to illuminate the proceed lamp G, but that when the grid circuit de-energized the tube D is rendered non-conductive to a suflicient extent to extinguish lamp (i.

The electron tube D is provided with a plate circuit which pasres from the right- 1 hand terminal of transformer secondar Y 16 through wire 37, step lamp R, wire 38, tube D wire 28, filament 5 of tube D, and wires and to the point 36 in secondary 16. It will be observed that at any given instant the polarity of the voltage applied to this plate circuit is opposite to the polarity of the voltage applied to the plate circuit of tube D, that is, when the plate 7 of tube D is positive with respect to the filament, the grid 6 of this tube is negative with respect to lihunent. It follows that the characteris tics of this tube are represented by the curve E in Fig. i when the grid is energized, and by the curve Ply/t) when the grid is deenergized. The voltage ot' the right hand portion of secondary 16 is higher than that of the left-hand portion, and 1 will assume that the voltage applied to the tube by the right-hand portion of the secomlary is the value t l f in Fig. 1. It follows that while the grid circuit. is energized the current. in the plate circuit for tube D is 1 in Fig. 1. which current is so small that stop lamp R is dark. lVhen the grid circuit is de-energized, however. a pulsating current represented by I, in Fig. l flows in the plate circuit for tube D, and this current is sutlicicnt to illuminate the stop lamp R.

\Vlicn the track section .\*B is unoccupied, the grid circuits for the tubes D and D are, of course, supplied with energy. The plate circuit of tube D is then rendered conductive to such an extent as to permit the proceed lamp G to be illuminated, but the plate circuit for tube D carries so little cur rent that lamp R is dark. Signal S then indicates proceed. When a car or train enters the section A- P). the grid circuits are de energized and the tube D is then rendered sufliciently non-conductive to extinguish the lamp G. At the same time, however, sufiicient pulsating current flows through the plate circuit of tube D to illuminate lamp B so that the signal S then indicates stop.

Referring now to Fig. 4, the apparatus comprises two electron tubes D and D as in Fig. Tube D is provided with a grid circuit which is supplied with energy from transformer H and which includes wires 24 and The grid circuit for tube D is supplied with energy in a different manner as will hereinafter appear.

The filaments of the electron tubes are constantly heated from transformer secondary 8, the circuit being from this secondary through wire 29, filament 5 of tube D wires 28 and 28*, filament 5 of tube D, and wire 31 to secondary 8.

The plate circuit for tube D is from the left-hand terminal of secondary 16, through wire 32, primary of a transformer L, proceed lamp G, wire 33, tube D and wires 31 and to point 36 on the secondary 16. The circuits associated with tube D are adjusted in the same way as the corresponding circuits in Figs. 2 and 3, so that lan'ip G is lighted or extinguished according as the grid circuit is energized or de-energized.

The secondary of transformer L is connected with the grid and filament of tube D by wires 39, 42 and 41, 28. Although the primary of this transformer is supplied with pulsating current, such current has an alternating component which will induce an alternating current in the secondary and this alternating current is in turn impressed across the grid and filament of tube D The secondary circuit of transformer L c0nsti tutes, then, the grid circuit for tube D Preferably a condenser is connected across the secondary ol' transformer L to balance the inductive reactance of this transformer. The reason for this condenser is as follows: The current in the plate circuit of tube D is substantially in phase with the impressed voltage because this circuit is substantially non-inductive, and by balancing the inductive reactance of transformer L with condenser 40 the secondary voltage, that is, the voltage applied to the grid circuit of tube D is brought substantially into phase with the voltage applied to the plate circuit of tube D which circuit will now trace.

The plate circuit [or tube D is from the right-hand terminal of secondary 16. through wire 37, stop lamp R, wire 38, tube D wires 28 and 28 filament of tube D. and wires 31 and 35 to point 36 in secondary 16. The voltage applied to this plate circuit is opposite in instantaneous relative polarity to the voltage applied to the plate circuit of tube D, and the plate voltage of tube D is represented by E3) in Fig. 1. Inasmuch as the grid voltage applied to tube D is substantially in phase with the plate voltage of tube tilt) D, which latter voltage is of the opposite instantaneous relative polarity to the plate voltage of tube D it follows that in tube D the grid is negative with respect to the filament at the same instant that the plate is positive with respect to the filament. The characteristics of tube D are, therefore, represented by curve Egwhen the grid circuit is energized, and by curve E90 when the grid circuit is de-energizcd. it will be seen, therefore, that when the grid circuit of tube D is energized, the current in the plate circuit of this tube is represented by I in Fig. l, which current is too small to light the stop lamp R; but that when the grid circuit is ole-energized. the current in the plate circuit. of tube D is represented by 1 in Fig. l. which current is suilicient to light the stop lamp B.

When the track section A l is unoccupied. the grid circuit for tube D is ener-- gized, so that lamp G is illuminated. The gird circuit for tube D is likewise encrgized at such times so that the current in the plate circuit for tube D is very small and lamp R is therefore extinguished. Signal S then indicates proceed. When a car or train enters section A--B. transformer H ceases to apply voltage to the grid circuit of tube D, so that this tube is rendered substantially non-conductive and the current in its plate circuit is consequently reduced to such value that lamp G is eXtinguished. 'lransformer L then practically ceases to apply grid voltage to the tube D so that current of suflicient value to illuminate lamp R then flows in the plate circuit for the latter tube. The signal S then indicates stop.

Referring now to Fig. 5, I have here shown a stretch of railway track which is divided by insulated joints 2 into a plurality of successive track sections A 8. B -(l, etc. Tratlic along this stretch normally moves in the direction indicated by the arrow. liocated adjacent the entrance end of each section a signal designated S with a suitable exponent. each of which signals. as here shown, comprises three lamps G. Y and R. adapted when lighted to indicate pro eed. caution and stop. respectively.

Each track section is provided with a track circuit con'iprising a transformer T. the secondary of which is connected acros: the rails at the exit end of the section. and a second transformer ll the primary of which is connected across the rails at the entrance end of the section. As will be explained hereinafter, means are provided for supply ing alternating current of one relative polarity or the other to the primary of each transformer T.

In the following description of appara tus and circuits I will refer specifically to the parts associated with signal S, but it is understood that such explanation and (lescription apply equally well to the parts as sociated with each of the other signals.

Located adjacent the signal S are three electron tubes D, D and I)", each of the three-element type coniprising a heated filament 5, a grid (3 and a plate 7. The tubes 1) and D are provided with grid circuit; which are energized from transformer H. The grid circuit for tube D is from the lefthand terminal of the secondary 62 of transformer II through wire 45, grid 6 and filament 5 of tube 1), and wires 48, 49 and 44 to the middle point of the secondary. The grid circuit for tube D is from the right hand terminal of the secondary 62 of trans forn'ier H. through wire 43. grid and filament of tube D wire 47, filament 5 of tube D, and wires 48, 49 and 44, to the middle point of the secondary. It will be seen, therefore, that when transformer H is supplied with current from the track rails. the grids of tube; D and D will at any given instant be of opposite polarity; that: is, when the grid of tube 1) is positive, the grid of tube 1) is negative. and, vice versa, this being due to the fact that the grids of these two tubes are connected with opposite terminals of the secondary 62 while the filament of each tube is connected with the middle point of this secondary.

Tube D is provided with a plate circuit which passes from the upper terminal of secondary 16 of transformer J, through the primary of a transforn'ier L lamp G. wire 46. tube 1), wire 47, filament. of tube D, wires 48. 49 and 50, primary of transformer T, and wire 51 to an intermediate point. 36 on the secondary 16. The voltage applied to this circuit by secondary 16 is represented by Fly) in Fig. l, so that when the grid cir cuit for tube D is de cnergized (F y in Fig. l) the plate circuit current ii 1 in Fig, l. and when the grid is negative with respect to the filament at the same instant that the plate is positive with respect to the lila nient (Fgin Fig. l) the plate circuit current is l in Fig. 1. Each of these currents is too small to light lamp G. \Yhen. however. the grid and plate are simultaneously positive with respect to the filament (Fir in Fig. 1) the plate circuit current i; l, n Fig. l and this: current. is suflicient to light lamp (i.

The plate circuit for tube l) s from the upper terminal of transformer secondary 16 through the primary of transformer I), wire 52, lamp Y, wire hi). tube l). wires 4th 49 and 50, primary of transformer T and wire 51 to point 36 in secondary 16. The characteristics of this circuit. are the same as those of the circuit for lamp G; that is, when the grid and plate of tube D are simultaneously positive with respect to the filament, sufficient current will flow in this circuit to illuminate lamp Y, but when the grid, and

lltl

llfi

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plate are simultaneously negative and positive, respectively, or when the grid circuit is (lo-energized, the current is reduced to such value that lamp Y is extinguished.

The electron tube D is provided With a grid circuit. which includes the secondary of transformer l1, this circuit being from the transformer secondary, through wire 54:, grid and tilament of tube D wire 58, filament of tube D wire 47, filament of tube D, and wires 1:5. and 55 to the secondary of transformer L. This circuit is preferably provided with a condenser for the same reason as in Fig. 4.

The plate circuit for tube D is from the lower terminal of transformer secondary 16, through wire 56, lamp R, Wire 57, tube D wire 58, tilament of tube Diwire 47,filament of tube D, wires 18, 49 and 50, primary of transformer T and wire 51 to point 36 in secondary 16. It will be observed that the grid circuit for tube D is energized When lamp (1} or lamp Y is illuminated, but not when these lamps are, both extinguished. The voltage, applied to the plate circuit for this tube by secondary 16 is considerably greater than the voltage applied to the plate circuits for the other tubes, owing to the fact that point 36 is not a middle point in secondary 16. That is, the plate voltage applied to tube 2 is represented by Ep" in Fig. 1. The grid and plate circuits for tube 1) are adjusted in the same way as the circuits for tube in Fig. 4, so that when either lamp t} or Y is lighted, lamp R will be extinguished, but that when both lamps G and Y are extinguished, lamp R will be lighted.

lt will be observed that when lamp G or lamp Y is lighted, the upper terminal of transl'm'mer secondary 16 is connected with the left-hand end of the primary of transformer T. so that current of one relative polarity is then supplied to the track rails of section A -B. Vhen lamp R is lighted, however, the lower terminal of secondary 16 is connected with the left-hand end of the primary of transformer T so that current of the other relative polarity is then supplied to the rails of section A-B. These polarities are such that when section BC is occupied by a car or train the relative polarity of the current supplied to section AB is such to cause current to flow in the plate circuit for tube D at signal S so that the caution lamp Y of this signal is lighted. \Vhen section llC is unoccupied, however, the relative polarity of the current supplied to section A-B is such as to cause tube D at signal S to be conductive so that the proreed lamp (l of this signal is illuminated.

As shown in the drawing, track section C-F is occupied by a car or train \V. The grid circuits for tubes D and D at signal C are deenergized, so that lamp R of this signal is lighted and lamps G and Y are extinguished. Signal S therefore, indicates stop. The relative polarity of the current supplied to transformer T C is then such as to render tube D at signal S conductive, so that lamp Y of signal S is lighted and lamps G and R are extinguished. It "follows that signal S indicates caution. Current of the other relative polarity is then supplied transformer T so that signal S indicates proceed.

Referring now to Fig. 6, I have here shown a means for controlling a signal lamp in such manner that the lamp is supplied with current on both halves of each wave of the alternating current source, one half being passed through an electron tube D and the other half being passed through a similar tube D This lamp may be the proceed lamp G or the caution lamp Y or the stop lamp R of the complete signaling systems shown in Figs. 5 and 7. The grid circuits for the tubes D and D are furnished with alternating current from a transformer H,

the primary of which is connected with the rails of track section A-B. Alternating current of one relative polarity or the other is supplied to the rails of this section from a transformer T through a pole-changer E which may be operated in any suitable manner.

The grid circuit for tube D is from the upper terminal of the secondary of transformer H, through wire 62, grid 6 and filament 5 of tube D, wires 63 and 64 in multiple, the two halves of secondary 8 in multiple, and wire 65 to the middle point of the secondary of transformer H. The grid circuit for tube D is from the lower terminal of the secondary of transformer H, through wire 66, grid 6 and filament 5 of tube D Wires 63 and 64 in multiple, the two halves of secondary 8 in multiple, and wire 65 to the middle point of the secondary of transformer H. It will be observed that at any given instant the polarity of the grid 6 of tube D is opposite to the polarity of grid 6 of tube D for the reason that these grids are connected with the two end terminals respectively of the secondary of transformer H, whereas the middle point of this secondary is connected with the filament- 5 of each tu e.

The plate circuit for tube 1) is from the left-hand terminal of the secondary 16, through wire 67, plate and filament of tube D, wires 63 and 61 in multiple, the two halves of secondary 8 in multiple, Wires 65 and 68, the signal lamp G (Y or R), and wire 69 to the middle point of secondary 16. The plate circuit for tube D is from the right-hand terminal of secondary 16, through wire 70. plate and filament of tube D wires 63 and 64 in multiple, the two halves of secondary 8 in multipe, and wires l Lt U and 68, the signal lamp, and wire 69 t0 the middle point of secondary 16. It will be observed that the plate 7 and the two tubes are connected respectively with the end terminals of transformer 16, so that at a given instant these plates have opposite polarities.

Assuming that the signal lamp is a proceed lamp Gr, the voltage applied to the plate circuit of each electron tube is represented by the voltage E1) in Fig. l. and the circuits are so arranged that normally the plate 7 and the grid 6 of each tube are simultaneously positive with respect to the filament of the same tube. \Vhcn the plate 7 and grid 6 of tube D are both positive with respect to filament 5, current will flow from the lefthand terminal of transformer secondary 16 through tube D and lamp G, but current will not flow through tube D because at such instant the plate 7 of this tube is negative with respect to the filament. During the next half wave of the alternating currents, the plate and grid of tube D are both positive with respect to the filament of this tube, so that current will flow from the right-hand terminal of transformer secondary 16 through tube D and lamp G, but it will not flow through tube D and lamp G. The grid of each tube being positive with respect to the filament at the same instant that the plate is positive with respect to the filament, the characteristics of the tubes are as represented by the curve Eg+ in Fig. 1, so that the current flowing in each plate circuit is the value I in Fig. 1. This current is sufficient to light the lamp G.

\Vhen the polechanger E is reversed, it is obvious that the grid of each tube is negative with respect to the filament at the same instant that the plate is positive with respect to the filament, so that the characteristics of each tube are as represented by the curve Egin Fig. 1. The current which then flows through lamp G is the value I in Fig. 1. which current is not sufiicient to light the lamp.

Assuming that the lamp in Fig. 6 is the caution lamp Y. the adjustments are the same as before, except that the connections to either transformer H or J are reversed so that the grid and plate of each tube are simultaneously positive with respect to the filament when the pole-changer E is in its reversed position.

Assuming now that the signal lamp in Fig. 6 is the stop lamp R, the plate voltages are increased to the value E19 in Fig. 2. Then when the grid circuits are deenergizcd, so that the characteristics of the tubes are represented by curve E in Fig. l, the plate currents will have the value 1 in Fig. 1, so that the lamp It will be lighted. The grid circuits are so arranged that when they are energized the grid of each tube is negative with respect to the filament at the same instant that the plate is positive with respect to the filament, so that the characteristics are as represened by the curve Eg in Fig. 1. It follmvs that when the grid circuits are energizcd, the current flowing through lamp Y has the value I in Fig. 1, which current is insufiicicnt to light the lamp.

In the case of either the proceed or caution lamp (2 or Y. when the grid circuits are tie-energized, as by a train in track section A-B. the characteristics of the tubes will be as rcprcscnted by the curve Eg/O in Fig. 1, so that the current will be of value 1 in Fig. 1, and this current is insufiicient to light the lamp.

Referring now to Fig. 7, I have here shown a complete signaling system similar to that shown in Fig. 5 but based on the fundamental circuit arrangement shown in Fig. 6. in that both halves of each alternating current wave arcv utilized by the signal lamps.

The proceed lamp G is supplied with current from a secondary 16 of transformer J and the circuit for this lamp is controlled by two electron tubes Dy, and Dg The cantion lamp Y of signal S is supplied with current from secondary 16" of transformer J and the supply of this current. is con lled by two electron tubes DJ and D Q.

The supply of current to the stop lamp It is furnished by a secondary 16 of transformer .l. and the supply of this current is controlled by two electron tubes 1),.1 and U L, which tubes in turn are controlled by trans l'ormcrs L and L associated with the circuits of lamps G and Y, res 'icctivcly.

The filament 5 of each tube is ctmstantly heated from the secondary b of the associattul transformer J. i

The plate circuit for proceed lamp tube D i passes from the left-hand terminal of secondary 16 of transformer J, through primary winding T1 of trz'instormer L. plate and filament of tube D 1, wires (53 and 64 in multiple, the two halves of secondary 8 in multiple, wire 65, winding of relay Z, lamp (1. and wire (39 to the middle point of secondary 1G. The circuit for the other proceed lamp tube D 2 includes primary winding 72 of transformer 11, the tube D 'J. rclay Z. and lamp G. Similarly, the plate circuit of tube D l begins at the left-hand terminal of s-ccondarv 16", passes through primary winding T1 of transformer L the tube I)y1. relay Z and lamp Y to the middle point of secondary 16". The plate circuit for tube D E passes from the right-hand terminal of secondary 16", through primary winding 72 of tramt'ormer L and tube Dd, winding of relay Z, lamp Y. to the middle point of sec ondary 1(3. The plate circuits for tubes D l and 1),.2 include the stop lamp R. but not the relay Z. These circuits will be understood from the drawing without further explanation.

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The track transformer T comprises a secondary which is constantly connected across the rails, and a primary which is supplied with alternating current from the secondary of transformer X. The primary of the latter transformer is connected across the transmission line i). The right-hand terminal of the secondary of transformer X. is constant ly connected with the middle point of the primary of transformer T. \Vhen relay Z is energized. the left-hand terminal of the secondary of transformer X is connected with the right-hand terminal of the primary of T and the current which then supplied to the rails of section A li is of what I will term normal relative polarity. \v'hen relay Z8 is tic-energized, the left-halal terminal of the secondary of transformer X is connected with the left-hand terminal of the a primary of transformer T and the current which is then supplied to the rails of section A-B is of what I will term reverse relative polarity.

The grid circuit for tube D l is from the left-hand terminal of the secondary of transformer It, through the grid and filament of l),;1, wires (33 and (3 in multiple, the two halves of secondary S in multiple, and wires and 73 to the middle point of the secondary of transformer H. The grid circuit for tube 1),;2 is similar, except that it includes the right-hand half of secondary of transformer ll. Similarly, the grid circuit for tube D l includes the right-hand half of the secondarv of transformer H, and the grid circuit for tube D E includes the left-hand half of the secondary of transformer H.

The plate and grid circuits of tubes D and D are so arranged that when current of normal relative polarity is supplied to the rails of section li -C the grid of each tube D is positive at the same instant that the plate of each of these tubes is positive, whereas the grid of each tube D is negative at the same instant that the plate of each tube is positive. \Vhen the instantaneous relative polarity in the rails of track section B C is reversed, so that this current is of reverse relative polarity, the grid of each tube D is negative at the same instant that the plate is positive, whereas the grid of each tube D is positive at the same instant that the plate is positive. It follows that when the current in the track rails is of normal relative polarity, both tubes D are conductive so that lamp G is lighted, whereas when the current in the track rails is of reverse relative polarity, both tubes Dy are conductive, so that lamp Y is lighted.

As shown in the drawin track section CF is occupied by a train JV, so that the grid circuits for tubes D l and D Q and D and D 2, at location C, are de-energized. The proceed lamp G and the caution lamp Y in signal S are, consequently,

extinguished. The grid circuits of 'both tubes D l and D Q are, consequently, de-energized, so that the currents in the plate circuits of these tubes are as represented by I in Fig. 1, and so it follows that. the stop lamp R is lighted. Signal S therefore, indicates stop.

Inasmuch as the currents flowing in the circuits for lamps G and Y of signal S are very small, relay Z is de-energized, so that current of reverse relative polarity is supplied to the rails of section B-(l. (lonsidering the apparatus at location B, the grids of tubes D 1 and D Q are negative at the same instant that the plates are positive, so that lamp of signal S is extinguished. The grids of tubes D l and D EZ are, however, positive at the same instant that the plates of these tubes are positive, so that lamp Y is lighted. Inasmuch as currents are now flowing in the primary windings 71 and 72 of transformer L it will be apparent that the grid circuits of tubes D 1 and D E are energized, but that the grid of each of these tubes is negative at the same instant that the plate is positive, so that the current in lamp R is of the value I in Fig. 1, and so that this lamp is extinguished. Signal S therefore, indicates caution.

Inasmuch as lamp Y of signal S is lighted, relay Z is energized, so that current of normal relative polarity is supplied to the rails of section A-B. Considering now the tubes at location A, it. will be apparent that the grid of each tube D l and D Q is positive at the same instant that the plate is positive, so that lamp G of signal S is lighted. As for tubes D 1 and D Q, the grid of each tube is negative at the same instant that the plate is positive, so that lamp Y is extinguished. Inasmuch as the primary windings 71 and 7 2 of transformer L are energized, the grid circuits for tubes D 1 and D Q are energized, so that the flow of current in lamp R is suppressed. It follows that signal S indicates proceed.

In the apparatus shown in Fig. 7 the supply of track circuit current to the track rails is controlled by relays Z, which relays have moving parts. If it is desirable to eliminate relays of this character, the supply of current to the track rails may be accomplished by means of the apparatus shown in Fig. 8. Referring to this View, the reference characters V, P and Q, designate three tItlIlS'fOlD'lGI'S, the secondaries of which are connected in series across the rails of section AB. The primaries of these transformers are connected in series across the secondary of transformer X The secondaries of transformers V, P and Q, are all connected in like direction, whereas the primary of transformer V is connected in opposition to the primaries of transformers P and Q. A third winding 76 and a third (iii winding 79 are rovided in transformers P and Q. which windings are connected in series with the common return from the proceed and caution lamps G and Y of signal S so that these third windings are energized whenever lamp G or Y is lighted. Thesc third windings 7G and 77 are oppositely connected, so as to balance or neutralize the alternating voltage induced in these windings by the other windings on the transformers. Since the primary currents are the same in transformers V. l and Q, and the secondary currents are likewise the same in these three transformers, the volt ages are proportional to the impedanccs of the transformers and these impedanccs are so chosen that when lamps G and Y are extinguished. the sum of the impedanccs of transformers P and Q, is greater than the impedance of transformer V. The electrical conditions will then be as shown in Fig. 9, from which it will be seen that a voltage of the value and relative direction indicated by the arrow 81 is supplied to the rails of section A-B. lVhen lamp G or lamp Y is lighted, however, the effect of the pulsating direct current in the third windings n; and 77 is to magnetize the cores of transformers P and Q and so to reduce the alternating current impedances of these transformers so that the sum of the voltages across their terminals will be less than the voltage across the secondary terminals of transformer V. The electrical condition is then as shown in Fig. 10. from which it will be noted that the voltage 81 supplied to the track rails of section A-B is reversed in instantaneous relative polarity. It follows, therefore, that the voltage supplied to the track rails is of one relative polarity when lamps (l and Y are both extinguished and of the opposite relative polarity when either lamp fir or Y is lighted.

Although I have herein shown and described only a few forms of railway taflic controlling apparatus embodying my invention, it is understood that various changes and modifications may be made therein within the scope of' the appended claims without departing from the spirit and scope of my invention.

llaving thus described my invention what I claim is:

1. In combination. a section of railway track provided with an alternating current track circuit: an electron tube having a heated filament. a grid and a plate; a grid cir- -nit for said tubc energized by said track circuit. a plate circuit for said tube including a source of alternating current so connected that the grid and plate are simultaneously positive with respect to the filament, a second electron tube similar to the first. a grid circuit for said second tube energized from the plate circuit of the first tube, a plate circuit for said second tube including a source of alternating current of higher voltage so connected that the plate of the second tube is negative with respect to the filament when the grid is positive with respect to the filament. and signaling mcans for said track section controlled by said piatc circuits.

2. in combination. a scction of railway track providcd with an alternating currcnt trach circuit an cicctron tube having a heat ed filament. a grid and a platc: a grid circuit for said tube energized by said track circuit. a plate circuit for said tube including a source of altcrnating current so conncctcd that the grid and plate arc sin ultaneously positivc with respect to the filament. a second clectron tube similar to the first. a grid circuit for said second fubc cnergizml from the plate circuit of the first tube. a plate circuit for said second tube iucliuling a source of aitcrnating current of higher voltage so con nectcd that the plate of the second tube is ncgativc nilh rcspcct to the filament. when the grid is positive with rcspcct to the filamcnt. a prococd signal included in said first plalc circuit. and a stop signal included in mid sis ond plate circuit.

$3. in combination. a section of railway track. a track circuit for said section includ ing a source of alternating current rcvcrsihly connccfcd with the rails; two clcctron tubes each having a heated filament. a grid and a plate: a grid circuit for each tube cncrgizcd from said track circuit in such manner that the grids have opposite polaritie at any given instant. a plate circuit for said tube including a source of alternating current and having two branches one for cach tube. a third electron tube having a grid circuit energized from the plate circuit of the first tubes. a plate circuit for said third tube including a source of alternating currentof higher voltagc than the first. and signaling mcans for said section controlled by said second platc circuit. and by thc two branches of the first plate circuit.

f. In combination section of railway track. an alternating current track circuit for said scction including a sourcc ol' currcnt rcvcrsibly connccted with the rails. two electron tubes cach provided with a grid circuit supplied with encig from said track circuit in such manncr that thc grids havc opposite polarities at any given instai t. a plate circuit for said fubcs including a sonrcc of current and thc primary of a transformer. said circuit having two branches one for each tube, a third electron tubc provided with a grid circuit energized from the secondary of said transformer. a plate circuit for said third tube including a source of alternating current. and signaling means for said section associated with said second plate circuit and with the two branches of said first plate circuit.

li t] 5. Railway trafiic controlling apparatus comprising a track circuit including a source of alternating current reversibly connected tl'ierewith. two electron tubes each having a grid circuit. supplied with energy from said track circuit in such manner that the two grids have opposite polarities at any given instant, a signal having three electric lamps adapted when lighted to indicate proceed, caution and stop respectively, means for normally supplying current to said stop lamp, and means controlled by said tubes for supplying current to the proceed or the ca ution lamp according as current of one relative polarity or the other is supplied to said track circuit and for simultaneously suppressing the supply of current to said stop lamp.

6. In combination, a section of railway track, an electron tube, train controlled means for said section for supplying a difference of potential to the grid and filament of said tube, a plate circuit for said tube, a second electron tube, a grid circuit for said second tube controlled by the fiow of current in the first tube, and signaling means for said section controlled by the plate circuits for said first and second tubes.

7. In combination a section of railway track, an electron tube, train controlled means for said section for supplying a differenee of potential to the grid and filament of said tube, a plate circuit for said tube, a second electron tube, a grid circuit for said second tube controlled by the flow of current in the first tube, and a proceed signaling device included in the plate circuit for the first tube and a stop signaling device included in the plate circuit for the second tube.

8. In con'ibination, a section of rail 'ay track, an electron tube, a grid circuit for said tube controlled by traffic conditions in said section, a plate circuit for said tube, a second electron tube, a grid circuit for said second tube controlled by the plate circuit for the first tube, a plate circuit for the second tube, and signaling means for said section controlled by said plate circuits.

9. In combination, a section of. railway track. an electron tube, a. grid circuit for said tube controlled by trafiic conditions in said section, a plate circuit for said tube. a second electron tube. a grid circuit for said second tube controlled by the plate circuit for the first tube. and signaling means for said section controlled by said tubes.

10. In combination, a section of railway track. an electron tube. a grid circuit for said tube controlled by tratlic conditions in said section, a second electron tube controlled by said first tube. and signaling means for said section controlled by said tubes.

11. In combination, a section of railway track, a track circuit for said section including means for reversing the instantaneous relative polarity of the current flowing therein, two electron tubes, grid circuits for said tubes controlled from said track circuit, plate circuits for said tubes, said grid and plate circuits being so connected that one tube or the other is conductive according as the track circuit current has one instantaneous relative polarity or the other, and two si nal lamps included in said two plate circuits respectively.

l2. In combination, a section of railway track, a track circuit for said section including means for reversing the instantaneous relative polarity of the current flowing therein, two electron tubes, grid circuits for said tubes controlled from said track circuit, plate circuits for said tubes, said grid and plate circuits being so connect-ed that one tube or the other is conductive according as the track circuit current has one in stantaneous relative polarity or the other, a signal comprising an electric lamp, and means controlled by said tubes for causing said lamp to be extinguished when either tube is conductive and lighted when neither tube is conductive.

13. In combination, a section of railway track, a track circuit for said section including means for reversing the instantaneous relative polarity of the current flowing therein, two electron tubes, grid circuits for said tubes controlled from said track circuit, plate circuits for said tubes, said grid and plate circuits being so connected that one tube or the other is conductive according as the track circuit current has one in stantaneous relative polarity or the other, a proceed signal device included in one plate circuit, a caution signal device in the other plate circuit, a stop signal device, and means controlled by said plate circuits for rendering said stop signal device operative when neither tube is conductive.

14. In combination, a section of railway track, a track circuit for said section including means for reversing the instantaneous relative polarity of the current flowing therein, two electron tubes, grid circuits for said tubes controlled from said track circuit: in such manner that the grids have opposite polarities at any given instant, a plate circuit for said tubes having two branches one for each tube, and a signaling device con uprising an electric lamp included in said plate circuit.

15. In combination. a section of railway track, a source of alternating current connected with the rails of said section, a transformer having a primary connected with the rails of said section, two electron tubes. means for connecting the grid and filament of one tube with one terminal and the middle point respectively of the secondary of said transformer, means for connecting the grid and filament of the other tube With the other terminal and the middle point respectively of the secondary of said transformer, a second transformer having its primary connected with a source of alternating current. means for connecting the plate and filament of one tube with one terminal and the middle point respectively of the secondary of said second transformer, means for connecting the plate and filament of the other tube with the other terminal and the middle point respectively of the secondary of said second transformer, the two plate circuits thus described having a common conductor between the middle point of the transformer and the tube filaments, and signaling means controlled by said common conductor.

16. In combination, two successive sections of railway track, a track circuit for the :t'orward section, an electron tube controlled by said track circuit, and means controlled by said tube for supplying current of one relative polarity or the other to the rails of the rear section.

17. In combination, two successive sections of railway track, a track circuit for the forward section. an electron tube controlled by said track circuit, a relay controlled by said tube, and means controlled by said relay for su 'iplying current of one relative polarity or the other to the rails of the rear section.

18. In combination, two successive sections of railway track, a track circuit for the forward section, an electron tube having a grid circuit controlled by said track circuit, and means controlled by the plate circuit of said tube for supplying current of one relative polarity or the other to the rails of the rear section.

19. In combination, two successive sections of railway track, a track circuit for the forward section, two electron tubes, grid circuits for said tubes controlled by said track circuit, plate circuits for said tubes, said grid and plate circuits being so connnected that one plate circuit or the other is conductive according as the current in the track circuit is of one relative polarity or the other, and means controlled by said plate circuits for supplying current of one relative polarity to the rails of the rear section when either plate circuit is conductive, and for supplying current of the other relative polarity to the rails of the rear section when neither plate circuit is conductive.

20. In combination, two successive sec tions of railway track, a track circuit for the forward section including a source of current reversibly connected with the rails, two electron tubes, grid circuits for said tubes controlled by said track circuit, plate circuits for said tubes having a conductor in common, said grid and plate circuits being so connected that one plate circuit or the other is conductive according as the current in the track circuit is of one relative polarity or the other, a relay included in said eom- 111011 conductor and arranged to be energized when either plate circuit is conductive but tie-energized When neither plate circuit is conductive, and means controlled by said relay for supplying current of one relative polarity or the other to the rails of the rear section according as the relay is energized or tie-energized.

In testimony whereof I afiix my signature.

LLOYD V. LEWIS. 

